As a molding drum, for example, a tire molding drum (in the following description, referred to simply as a drum), there is known a drum in which its circumferential surface is constituted by a plurality of segments which is divided, each segment is mounted at a tip end of a plurality of expandable arms radially extending from a center axis of the drum, and a tire constituent member is molded so that a gap is not generated between the segments when the arm is extended.
When such a drum is used, there is no problem as long as an inner diameter of a tire to be molded has such a size that a gap is not generated between the segments, but a gap is naturally generated between the segments.
When a gap is generated between the segments, there occurs a failure such as a defect in uniformity of a product tire or such that the tire constituent member wrapped around the drum falls into the gap.
Accordingly, a plurality of types of tire constituent members with different tire sizes (inner diameters) cannot be molded using one drum.
Therefore, conventionally, a drum fitted with a tire size for every tire different size is prepared, and the drum is selected each time the tire size is changed.
However, in this method, in addition to an aspect of cost by preparation of a plurality of types of drums, there is generated a work of changing the drum each time the tire size is changed, which becomes a hindrance factor of productivity enhancement in molding of the tire constituent member.
As a measure against this problem, for example, there is known a drum that is provided with first and second segments having different circumferential lengths, and that can be used for molding two tire constituent members with different inner diameters by making a selection from two drum diameters, that is, a drum surface having a first diameter formed by the first segment and a drum surface having a second diameter formed by the second segment (refer to PTL 1).
However, a drum configuration of Patent Literature 1 can be applied only to molding of two tires each having different inner diameter, and its effect is limited.